Efficient and accurate diagnosis of pathological agents (pathogens) is critical for clinical care, surveillance activities, outbreak control, pathogenesis, academic research, vaccine development, and clinical trials.
A variety of serological assays for identifying immune responses to pathogens have been documented, including, for example, serum neutralization (SN) assay (1), immunofluourescence assay (IFA), complement fixation assay (2), enzyme-linked immunosorbent assay (ELISA), and multiplexing technologies. These assays all follow a common set-up: the antigen/pathogen is used directly in the assay or is coated/coupled on a solid surface/platform to be used for antibody detection. However, these assays usually fail especially if crude or native pathogens are used. Failure can be due to high background and cross-reactivity combined with reduction of specificity and/or sensitivity of the assay, or overall poor analytical sensitivity (lower limit of detection) of the test.
Improvements to the serological assays have been made by using recombinant proteins or synthesized peptide to reduce the background issues. However, these methods have disadvantages as well such as high costs to produce consistent qualities and high quantities of recombinant proteins or antigenic peptides. These assays also use the protein or peptide directly coated/coupled to the solid surface of the assay, which can result in a poor accessibility of certain parts of the proteins.